You'll never need to change the ehfimech, the ehfisubstrat might need replacing after 10 years .... maybe even longer. There's only some slight mechanical degradation of the ehfisubstrat to worry about, so it's topping up rather than replacing.
I have so far rinsed out my 2026 and 2126, 5 or 6 times each over the past year or so and I've also simply rinsed out and reused both the white fine filter pad and the blue coarse filter pad. the blue pad would probably last quite a few years, the fine pad would go no more than 10 rinses I guess.
If you were to set up another Eheim can on another tank you might consider kick starting the cycle by taking some of the media from an existing can, swapping out with the new.
